'05 Envoy 4.2L LLM Low Pressure

[Sport45]

Hi, our '05 Envoy 4.2L will often indicate low (no actually) oil pressure at hot idle. This started a couple years ago and I changed the oil pressure switch. That took care of the problem until recently when it cropped up again. Generally, dropping it into neutral will raise the rpm enough to make it read pressure or I can just give it a little gas while my foot is on the brake pedal.

For those who don't know the oil pressure gauge just displays a calculated amount based on rpm, temperature and I don't know what else. The pressure switch just tells the computer it's okay to calculate a pressure.

I'm away from the thing now but intend to hook up an analog gauge to the test port on the filter housing in the next couple of weeks. If I find the pressure is dropping below the 7 or so psi switch setpoint I'd like to try a heavier oil to raise the hot pressure.

Okay, after all that my question is this: Would their be any detrimental effects to running a gas rated 15W40 in place of the 5W30 I've been using in this 135,000 mile vehicle? I don't intend to keep it more than another 9-12 months so an oil pump is out of the question. If the analog gauge shows adequate pressure at idle I'll just replace the switch again.

 

[bigt61]

Just run 15W-50 M1 and call it a day. Or go cheap and run 20W-50 SuperTech conventional.

 

[HerrStig]

That pressure measuring system sounds like it was created by a government bureaucrat. An analog gauge would be nice.

 

[jorton]

At hot idle how long does it take for the engine to get noisy? With no OP it should sound like a dry cold start that can occur after an oil change.

 

[Triple_Se7en]

Originally Posted By: bigt61
Just run 15W-50 M1 and call it a day. Or go cheap and run 20W-50 SuperTech conventional.


I don't suggest doing that.
If your engine is quiet at hot idle, do nothing at all. Factory dash pressure gauges are not accurate most times.

If you cannot sleep worrying about it, put in 10W30 and a 8oz bottle of oil treatment. That will improve idle readings and still offer you good oil flow.

 

[92saturnsl2]

Originally Posted By: HerrStig
That pressure measuring system sounds like it was created by a government bureaucrat. An analog gauge would be nice.


At least it's one step above Ford's dummy gauges, though equally as useless.

The Ford oil pressure sensor either reads above or below the preset pressure (5psi or thereabouts) and tells the gauge either to go to normal (usually around 2/3 to the top) or show zero. There's no in between, not correlated with temperature. I miss the GM gauges of days past, and even the good Ford OP gauge setup hasn't been around since the mid 80's.

I like the modern electronic info center that displays a digital oil pressure. I've seen them in newer Chryslers like on the Pentastar engines and they seem pretty darn accurate. Not sure if Ford or Chevy / others do this too.

 

[Nick1994]

It could easily be a bad switch again. Replace it

 

[bigt61]

In Texas, the 15W-50 will work fine. I used it year round here in N Va in my Suburban. OP said he was going to put a gauge on it anyway, so if it's a little low a thicker oil is a cheap way to make it last.

 

[KL31]

Try the proper gauge first and then see what the real readings are. Then go to a 40 grade if needed and see what happens.

 

[Sport45]

Thanks for all the responses! No, it doesn't make any noise (other than the check engine chime) when the gauge drops to zero. If I was hearing lifters collapse, etc. I wouldn't drive it. So I don't think I'm actually losing all oil pressure. I figured going to 40 weight(hot) oil would help if the analog gauge shows the idle pressure to be just below the trip setting of the switch. I am more worried about going from a 5 weight(cold) to a 15 weight for startup.

I've never liked 10W40 oils for the amount of polymers added to get the hot performance. 15W40 isn't nearly the stretch and that weight is available in gasoline rated oils.

But I'll still wait until I have rigged a temporary mechanical gauge for diagnosis. Don't know yet if I'll tape it to the windshield or try to find a firewall penetration to feed the line through...

 

[Sport45]

I like the sound of this. What oil treatment would you suggest?